Absorption refrigeration system

ABSTRACT

An absorption refrigeration system formed in substantially its entirety from at least two superimposed sheets bonded at their interfaces except for the portions defining operating components and interconnecting passages which are in outwardly expanded or embossed form, so that mass production techniques may be applied to the fabrication of the system.

Waited States Patent 1191 Meess et a1. 1 51. Jan. 1, 11974 [5 1 ABSORPTION REFRIGERATION SYSTEM 2,360,834 10 1944 Kogcl 62/490 2,690,058 9/1954 Backstrom 1 62/490 X [75] lnvemms: Jack Meess EXPO"; 2,855,766 10/1958 Elfving et a1 62/493 Kasmmhg Delmom; Robert 2,900,807 8/1959 s611e Jr. eta1..... 165/170 x y, Pittsburgh, all of Pa. 2,974,498 3/1961 Ehrenfreund 62/523 x Assigneez Westinghouse Electric p on, 2,979,310 4/1961 Nicholson 62/623 X Pittsburgh, Pa. Primary ExaminerWil1iam F. ODea [22] led: May 1969 Assistant Examiner-Peter D. Ferguson 2 App]. 324,114 Attorney-F. H. Henson and E. C. Arenz [52] US. Cl 62/476, 62/490, 62/491, [57] ABSTRACT [5 1] Im Cl 62/493 62/494 Ig An absorption refrigeration system formed in substan- [58] Fieid 490 491 tially its entirety from at least two superimposed 3 sheets bonded at their interfaces except for the por- A tions defining operating components and intercon- [56] References Cited necting passages which are in outwardly expanded or embossed form, so that mass production technlques UNITED STATES PATENTS may be applied to the fabrication of the system. 2,243,903 6/1941 Hintze 62/490 2,304,876 12/1942 Benson 62/523 X 7 Claims, 17 Drawing Figures PAH NIHJ 1 3, 782 a 1 34 SHEEI 1 BF 6 Fig.1

INVENTOR Jock D. Meess, n C. Kosfovlch v and ert S. Lackey ATTORN 1 ABSORPTION REFRIGERATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to the art of absorption refrigeration apparatus of integral tube-in-sheet character.

2. Description of the Prior Art It is well known to make heat exchange units from metal sheets processed and bonded in facing relation with a pattern of passages (typically inflated) provided between the sheets. The use of a panel of this general character in an absorption refrigeration system has also been suggested in the patent art as evidenced by US. Pat. No. 2,243,903. That patent deals with a tube-insheet type of absorption refrigeration apparatus which purports to comprise a complete absorption refrigerating apparatus in which the entire system is formed by the depressions of the metal sheets arranged face to face together. It is said that in that manner all or the majority of the vessels may be made of very few metal sheets. The result according to the patent is especially favorable for the mass production of absorption refrigcrating apparatus. However, the arrangement according to that patent is deficient, as contrasted to the present invention, in requiring certain auxiliary parts such as a pump and certain connecting conduits which must be separately manufactured and connected with the vessels and passageways formed of the metal sheets.

SUMMARY OF THE INVENTION Our invention provides a tube-in-sheet panel comprising the entirety of an absorption refrigeration apparatus, save for a source of heat and optional external heat exchange parts, the panel being constructed and arranged that as formed all of the operating components and fluid passageways interconnecting the components lie in the general plane of the panel so that no passageways nor components are external to the general plane of the panel as formed, and so that all of the components and passages are formed in the fabrication of the panel itself.

The invention is, in large part, concerned with problems and restrictions that are not present in a welded tube absorption refrigeration system which has been the conventional mode for making a small, inert gas, ammonia absorption refrigeration system. The main problem arising in providing a-tube-in-sheet absorption refrigeration system which is embodied in its entirety, insofar as its internal components and passages are concerned, in a planar panel as formed, is that the system design must be developed from what is essentially a two dimensional schematic pattern of the absorption refrigeration cycle. In other words, the physical location and relationships of the various basic components of -the absorption apparatus (condenser, evaporator, absorber and boiler) are located as though the system represented a flow diagram with gravity feed characteristics. Accordingly, cross-over tubes which would require additional welding, and three dimensional bends, both of which are common in welded tubular systems, are not permitted. Another limitation is that the width and height of the panels is limited by the machine facilities reasonably available for fabricating the panels. Also, the passages obtained in a hydraulically inflated panel are not fully round but approach an elliptical cross section with about a three to four, height to width ratio. Also, limitations deriving from the fabrication technique such as minimum bend radiuses and minimum bonding areas between passages are imposed.

DRAWING DESCRIPTION FIG. 1 is a face view of one currently preferred panel according to the invention in which evaporator and gas heat exchanger section have been displaced out of the general plane of the panel after formation of the panel;

FIG. 2 is a top view of the panel showing the relation of the displaced portion of the panel to the remainder of the panel;

FIG. 3 is a fragmentary face view of the upper part of the panel showing the evaporator and gas heat exchanger section before displacement;

FIG. 41 is a fragmentary sectional view of the typical junction between a vapor feed tube and a pump lift tube of the prior art type in which circular welded tubes are used;

FIG. 5 is a fragmentary sectional view of the same junction as that of FIG. 4 illustrating a junction arrangement which may be provided in a tube-in-sheet panel and which avoids the need for a separate piece to form an orifice;

FIg. 6 is a vertical sectional view corresponding to one taken along the line VI-VI of FIG. 5;

FIGS. 7 and 8 are fragmentary face views of alternate evaporator and gas heat exchanger section arrange ments which may be incorporated in a tube-in-sheet panel according to the invention;

FIG. 9 is a fragmentary face view of a preferred return bend arrangement in a tube-in-sheet panel in which liquid dams are provided;

FIG. 10 is a fragmentary face view showing a preferred configuration of the junction between the carrier gas line and the refrigerant delivery line with the inlet of the evaporator to control the direction of flow of the liquid refrigerant into the evaporator;

FIG. 11 is a cross sectional view of a typical conduit normal to the direction of fluid flow, and illustrating the general elliptical shape of the typical conduit formed in the tube-in-sheet panel;

FIG. 12 is a fragmentary face view of the portion of a panel incorporating an alternate form of reservoir as compared to that of FIG. 1; 3

FIG. 13 is a face of a fragmentary portion of a panel incorporating a boiler and lift pump section in a disposition reversed relative to the disposition of that section in FIG. 1;

FIG. 14 is a face view of a panel according to the invention in which three metallic sheets are joined in superimposed relation, with the intermediate sheet having strategically located openings therein to provide communication between inflated passages formed in the sheets on opposite sides of the intermediate sheet;

FIGS. l5, l6 and 17 are sectional views taken along the correspondingly designated lines of FIG. 14.

DESCRIPTION OF PREFERRED EMBODIMENTS The method of fabricating tube-in-sheet panels is well known and may be carried out by several processes. In one process, such as that of the Olin Mathieson Chemical Corporation, a stop weld masking paint is silk screened in the desired pattern to one of the two sheets to be bonded together. Then in a series of steps, the sheets then are passed through a rolling mill under sufficient pressure and at sufficient temperature to bond the sheets together in the unmasked area,

and a hydraulic connection is made to the unmasked area and the sheet inflated between two platens to form the desired passages. In another process in which no masking material is used, the two sheets are rolled together and some initial bonding is made over the entire interface. After proper heat treatment, hydraulic inflation is performed in dies designed so that the sheets are constrained except in those areas where the initial bond must be broken to inflate the passages. The sheets are then subjected to a final heat treatment which completely fuses the unbroken bond by diffusion. This later process is typical of that of the Texas Instrument Company.

In either of the cases above, the dies or platens required in the processes are relatively inexpensive if they may be designed to be generally planar, and if any forming or bending operations are made on the sheets after the inflation.

The currently preferred material from which the tube-in-sheet panel is fabricated is mild low carbon steel. The panel can also be fabricated from stainless steel but this is relatively expensive and accordingly in direct opposition to one of the main objects of the invention. Aluminum, copper and brass are not chemically compatible with the currently preferred ammonium hydroxide working fluid.

SYSTEM AS A WHOLE AND GENERAL OPERATION Absorption refrigeration panels according to the invention include the same general components, and operate in the same general fashion, as the typical absorption refrigeration systems of the uniform pressure type. As such, the systems use a refrigerant, an absorbent, and an auxiliary, pressure-equalizing gas. The uniform pressure system is also known as the Platen-Munters System, and sometimes as the Servel-Electrolux System, and as such utilizes a low molecular weight inert gas such as hydrogen which permits the overall system to operate at the same total pressure.

As shown in FIG. l, the panel includes the typical operating components including a generator or boiler 10, rectifier 11, condenser 12, evaporator 13, gas heat exchanger 14, absorber 15, liquid heat exchanger 16, and receiver or reservoir 17.

The parts of the boiler section and its general method of operation are as follows. The boiler section as a whole is thermally insulated from ambient. Heat is applied to the portion of the boiler section designated by the'dash-line outline 18 either electrically or by a flame to heat the lower portion of the riser tube 19 and portions of the vapor feed tube 20 and pump lift tube 21. This results in a vapor mixture of ammonia and water being driven through the feed tube to the junction of the lift tube and line 22 of the liquid heat exchanger 16, the line 22 carrying a rich ammonia solution from the reservoir 17. The boiler section also includes the return feed line 23 which connects to the riser tube 19 at an intermediate location through the trap tubes 24.

This general type of boiler is known as the influx type and differs from the general class of boiler which uses a heated straight pipe to initiate vapor bubbles and pumping action. The difference is that in the influx there is no vapor generation in the pump tube itself, with all of the vapor being generated in the riser tube 19. The influx type boiler is used advantageously on smaller units, with which the invention is principally concerned, since it provides economy and the advantage of being relatively insensitive to the location of the point of heat application to the riser tube 19, this latter advantage being of significance where flame heating is being used since the flame location is not controllable as accurately as is the location of an electric heater.

The vapor mixture of ammonia and water fed to the lift tube 21 from the feed tube 20 carries rich ammonia solution up the lift tube to the rectifier section 11 lower portion where the rich ammonia liquid solution separates from the vapor mixture to pass back through the return line 23 to the riser tube. The vapor mixture passes up through the rectifier section where water vapor is condensed out and also returned through line 23 to the boiler.

It is noted that with the influx boiler arrangement shown that the vapor mixture leaving the riser tube 19 (usually consisting of about 65 percent ammonia and 35 percent water vapor) is cooled and mixed with the rich liquid solution being elevated in the pump lift tube 21. Thus all of the vapor leaving the riser tube is utilized in the lift tube and much of the excess water vapor in the vapor mixture is condensed back into solution and returned to the boiler section without having to pass first into the rectifier. Accordingly, the vapor delivered to the rectifier will be in the order of approximately percent ammonia vapor and I0 percent water vapor so that a smaller rectifier section amy be used. This mixing of the hot vapor in the pump lift tube with the cooler ammonia solution is referred to as a mixing type analyzer, which may be provided in other ways than shown, but in the way shown is considered to function quite satisfactorily in the environment of a panel according to the invention. The influx boiler arrangement shown will also provide a lift to head ratio of up to 6 to I. This is advantageous since it does not require that a large part of the height of the sheet be used for the reservoir, which accordingly leaves more space for the refrigeration contributing components.

The rectified vapor passes through the condenser 12 where it is condensed in a conventional manner. The liquid ammonia exiting from the condenser flows by gravity through line 27, the lower portion of which is incorporated as a part of the gas heat exchanger 14, the liquid ammonia entering the evaporator at the three wayjunction 29 (which will be discussed in more detail in connection with FIG. 10). At the junction, the liquid ammonia begins to evaporate and diffuse into the inert gas which is at such a partial pressure as to produce a refrigerating effect in the evaporator. The inert gas is introduced into the inlet of the evaporator at the junction 29 from the line 30 which is in communication with the upper pass of the absorber 15, an intermediate portion 31 of the line 30 also being incorporated as a part of the gas heat exchanger 14.

The evaporator 13 arrangement shown in FIG. 1 is of two pass character with the outlet of the evaporator being in communication with the lower portion of the absorber 15 through line 32 which also includes a portion thereof forming part of the gas heat exchanger 14. The line 33 connects the line 32 to the outlet of the condenser 12 and functions as a vent or pressure equalizing line.

The absorber functions conventionally by accommodating a counterflow of liquid and gases. Weak ammonia solution from the lower portion of the riser tube 19 of the boiler section 10 passes through line 34, a portion of which forms part of the liquid exchanger 16, to the upper portion of the absorber where it descends through the numerous absorber passes to the reservoir 17 in communication with the bottom portion of the absorber. Rich ammonia gas and inert gas enter the bottom portion of the absorber from line 32 and ascend through multiple passes of the absorber passing over the descending weak ammonia solution so that the ammonia is absorbed back into solution to form a richer ammonia solution which is received into the reservoir 17 for subsequent flow through line 22 of the liquid heat exchanger 16 to the junction 25 with the pump lift tube 21. Ideally, all of the ammonia gas has been removed from the inert gas at the gas outlet 35 of the absorber.

These circulating paths for the components of the solution are conventional for any ammonia absorption system utilizing an inert gas. Thus the inert gas flows from the upper, gas outlet location 35 of the absorber through the line 30 to the inlet junction 29 of the evaporator, downwardly through the evaporator 13 and through line 32 to the bottom, gas inlet location 36 of the absorber, and back up through the absorber to the gas outlet location 35 to complete the loop.

A liquid absorbent loop is set up among the absorber, reservoir, liquid heat exchanger, and boiler. Rich ammonia solution leaves the lower portion of the reservoir and passes through the liquid heat exchanger by way of line 22 to the pump lift tube 21 where it is elevated in slugs by the ammonia vapor fed through the vapor feed line 20. The somewhat weakened ammonia solution passes by way of return tube 23 to the boiler riser tube 19 where vaporous ammonia is driven off, the weak ammonia solution passing from the lower end of the riser tube through the line 34 of the liquid heat exchanger back up to the liquid inlet location 35 of the absorber. The weak ammonia solution descends by gravity through the absorber counterflow to the rising ammonia vapor and inert gas, the enriched ammonia solution then being received by the reservoir 17.

Also of course, ammonia vapor fed to the condenser 12 is condensed into liquid ammonia and passed through the line 27 in liquid form to the inlet junction 29 of the evaporator. In the evaporator the liquid ammonia evaporates to perform its cooling function and then passes through line 32, along with the inert gas, down to the gas inlet location 36 of the absorber for its ascent in the absorber and absorption by the weak ammonia solution descending through the aborber in counterflow relation.

An inflation and charging port 26 can conveniently be provided to extend from the edge of the sheet to one of the tubes such as the return tube 23. The charging concentration can be between about 30 to 37 percent weight of ammonia to weight of water, which gives a working concentration of between aobut 28 to 31 percent depending upon temperature. This is of course a guide only, since the storage factor as well as pumping characteristics will determine the optimum level.

As has been noted, the circulation patterns and the general operational mode of the panel system according to the invention corresponds to that of the conventional inert gas type systems. However, the provision of the system as a whole in generally planar form for fabrication purposes, the omission of operating components (such as pumps) connected to the internals of the system, the size limitation imposed by present fabrication techniques for tube-in-sheet panels, and the requirement of obtaining reasonably satisfactory performance of the system, pose substantial problems in the design of the system as a whole. The approach taken in accordance with the invention in solving as many of the problems as possible is that of providing improvements in various of the components and their relationships such that each incrementally contributes toward the collective satisfactory result. However, the limitations imposed by the type, size and operating characteristics of the system involved results in at least some of the features affecting other parts of the system.

Thus the description following will deal for the most part in detail with parts of the system which are of at least some importance to one or another aspect of the invention.

It is noted that most of the work from which the invention resulted has been in connection with a panel having an overall dimension of about 24 inches wide and about 28 inches high, these dimensions lending themselves to incorporation of the system in certain small appliances such as portable refrigerators or other small refrigerators adapted to use a flame source of heat or a limited electrical source of heat. Accordingly, to the extent that values and dimensions are specified in the description, these relate to units of approximately the noted size, although the general concepts of the invention are not considered to be limited to any substantial degree to a particular size panel.

THERMAL BREAKS AND DISPLACED PORTIONS It will be appreciated that for the system to function satisfactorily to effect cooling that certain parts such as the evaporator must be thermally isolated to some degree from other parts operating at substantially higher temperatures. Further, it is necessary for reasonable efficiency that the other parts, which may be adjacent to each other on the panel as formed but which function at different temperatures, be thermally isolated. The cut lines which function in part as thermal breaks are indicated by the heavily shaded lines in FIGS. l and 3. These cut lines for example, separate each successively higher pass of the absorber from the pass immediately therebelow. The receiver or reservoir 17 is separated from the liquid heat exchanger 16 immediately therebelow by a cut line, which also extends up vertically between the right side of the absorber 15 and reservoir 17 to separate or isolate these parts from the boiler section and to isolate the rectifier 11 section.

The evaporator 13 and gas heat exchanger 14 are also displaced out of the general plane of the panel as a whole as formed, after formation. To this end, and as shown in FIG. 3, the U-shaped cut line 38 is provided to separate the condenser from the evaporator, and the evaporator from the gas heat exchanger, and the cut line 39 is provided to separate the gas heat exchanger from the underlying absorber. The evaporator and gas heat exchanger are then displaced to the position shown in FIG. 2 relative to the panel as a whole. It will also be appreciated of course that the cut lines not only function to thermally isolate parts, but also can be strategically located to reduce the restraint upon a fuller inflation of the passages during the pressurization of the entire circuit to achieve the desired local inflation of the passages to their specific sizes.

It is also noted that the provision of fins or other means for promoting heat transfer between certain of the operating components and the atmoshpere thereabout is not only desirable but normally necessary for satisfactory performance. As an example of this arrangement, if the panel of FIG. I were to be incorporated in the door of a small refrigerator for example, the fins designated 40 are applied to the face of the evaporator which is in heat exchanger relation with the interior of the refrigerator, while the fins 41 are applied to the opposite face of the condenser, and the absorber to promote heat exchange with the ambient in which the refrigerator is located. Since one potentially fruitful application of the system according to the invention is in connection with locations where electrical power may not be available, it is highly preferable that in such a case the system be operable with satisfactory performance without forced air flow.

PUMP LIFT TUBE FEED (FIGS. 4-6) The conventional practice with influx type pumps used in inert gas ammonia absorption refrigeration systems of the circular, welded tube types has been to employ a flow orifice 250 (FIG. 4) in the vapor feed tube 20a and the pump lift tube 21a. This arrangement does not pose any particular problem with the circular, welded tube type system since the orifice may be provided by simply drilling a hole in the side of the tube 21a before welding the end of tube 20a thereto. However, the provision of an orifice in the inflated panel type of construction in accordance with the invention is inconsistent with the aim of the invention in the respect of providing a completed system in the panel itself.

While an alternate boiler and pump system is possible, using a heated tube as a lift pump, such a boiler and pump would be inferior to the influx type arrangement since the influx type provides a relatively large lift-toheat ratio which permits the pumping of the aquaammonia to relatively high levels with small driving potentials. This lift ratio is relatively important in a panel system due to the inherent geometry ofa panel system. Also, the current manufacturing processes for the inflated panels precludes the use of passages smaller than about 0.190 inches (from corner-to-corner of the passage cross section), while the opening of the orifice for the circular, welded tube type of system having tube diameters substantially corresponding to the equivalent hydraulic diameters of the tubes of the panel system require an orifice opening of about 0.080 inches. Thus the orifice section may not be provided by simply arranging the sheets in the junction area to inflate to only the equivalent of 0.080 inches. An alternative way to provide an orifice section, after the inflation of the tubes, is to include a protuberance (not shown) on the tube 21 (FIG. 5) on its side opposite the connection of the vapor feed tube at the location designated 43. The end of the protuberance is sliced off and an orifice tube inserted therethrough, welded in place, and the protuberance then welded shut. It will be appreciated however that this arrangement is inconsistent with providing a system as a whole in the inflated panel itself.

In accordance with the invention, it has been discovered that by providing a junction as indicated at in FIG. 5, with the generally elliptical cross section as shown in FIG. 6, a functional orifice is effectively formed at the location indicated as 44 between the surface of the liquid 45 and the inside radius (of acute angle shape in cross-section) formed between the vapor feed tube 20 and the pump lift tube 21. It is here noted that while the cross-sectional shape of the tubes or conduits in the panel as inflated is generally elliptical (FIGS. 6 and 11), the shape also includes the acute angle corner portions at the opposite ends of the major axis beyond the normal curvature found in a true ellipse. The performance experienced with the FIGS. 5 and 6 arrangement has been at least equal to that obtained by employing a welded insert orifice plug, and it will be also appreciated that the arrangement of providing an orifice in this way is compatible with the invention as a whole.

EVAPORATOR AND GAS HEAT EXCHANGER CONFIGURATIONS (FIGS. 1, 7 and 8) The physical locations and relationships of the various operating components of a panel system according to the invention are limited to a substantial degree, as noted before, because of the various requirements such as gravity flow, thermal breaks, displaceable portions, and current panel fabricating limitations, for example. This is further complicated, as to the evaporator and gas heat exchanger section, by the practical necessity of providing a gas heat exchanger to obtain at least a reasonable efficiency. It will be appreciated of course that the gas heat exchanger 14 provides cooling between the rich gas leaving the evaporator and which is still relatively cool (e.g. 25F), with the liquid ammonia moving from the condenser to the evaporator inlet, and the weak ammonia gas and inert gas rising from the absorber upper portion to the inlet of the evaporator.

The evaporator and gas heat exchanger sections shown in FIGS. 1, 7 and 8, illustrate three ways in which, in accordance with the invention, these components may be provided in a panel system without requiring external crossovers or welded connections. The arrangement in FIG. 1 is the preferred arrangement where the panel height is greater than the width, while FIGS. 7 and 8 are concerned with the arrangements in which the width of the panel is greater than the height. In each of the arrangements it will be noted that there is a heat exchange relation between the three conduits which make up the gas heat exchanger. It will further be appreciated that in the prior art circular welded tube absorption systems that the provision of triple conduit heat exchange may be conveniently handled by coaxial tubes.

In FIG. 1 the condenser is of two pass construction and accordingly the feed of the liquid ammonia from the condenser to the inlet 29 of the evaporator is from right to left, as would be the case with any even number of passes. In the cases of FIGS. 7 and 8 arrangements, in which the width of the panel is greater, so that the condenser is typically a one pass (or odd number of passes) arrangement, the feed in the lines 27b and 27c from the condenser to the evaporator inlets 29b and 290, respectively, is from left to right.

In the FIGS. 1 and 8 arrangements the rich gas lines 32 and 32c are located between the liquid ammonia lines 27 and 270, and the inert gas feed lines 30 and 30c, while in FIG. 7 the rich gas line 32 underlies the inert gas line 30b and the liquid ammonia line 27b. However in each case the heat exchange relation exists between all three of the lines because of the unbroken heat conducting portions of the panels between the lines.

In the arrangement of FIG. 8, since the liquid ammonia line 27c joins the evaporator at an inlet location 290 from a level below the inlet of the evaporator, the trap arrangement or inverted trap arrangement of the inert gas feed lines 30 and 30b, seen in FIGS. 1 and 7, is not necessary. The reason for the inverted trap arrangements in these feed lines will be dealt with in connection with FIG. 10.

LIQUID DAMS AND RETURN BEND .CONFIGURATIONS (FIGS. 1 and 9) It is desirable in both the evaporator and absorber to provide means for disturbing the tendency for steady or uniform flow along the bottom of the tubes to enhance the evaporation process in the evaporator, to break up the surface film of rich liquid which tends to form when ammonia is absorbed in the absorber, and to increase the liquid-gas interfacial area in the absorber. In both the evaporator and absorber these means may take the form of a series of small dams, indicated by the numeral 46 (FIG. 1) in the evaporator and the numeral 47 in the absorber.

In a panel having overall dimensional limitations as noted'before, and where it is desired to obtain a given cooling capacity, it will be appreciated that to obtain an adequate passage length in both the evaporator and absorber it is necessary to provide a serpentine arrangement with end bends. For example, a sheet or panel intended to have about 30 watts cooling capacity requires about 25 inches of evaporator passage and nearly 84 inches of absorber passage. Thus, if the system is to be incorporated in a panel having a width of no more than 24 inches, a substantial number of end bends are necessary.

Finally, in the fabrication of a tube-in-sheet panel, it is recommended practice to provide a reasonable area of material between passages when making a return bend. For an arrangement of the capacity with which this description is concerned, an inside bend radius of H4 inch is recommended to avoid the possibility of stress concentrations.

In accordance with the invention, a saving in height of the panel is obtained without sacrificing structural integrity or function by strategically locating those dams at the end bends in accordance with the showing in FIG. 9. By incorporating that dam portion as a continuation of the inside radius of the end bend the height of the dam itself may be saved at each end bend. If the dams are about 1/8 of an inch high, in an arrangement such as shown in FIG. 1 almost an inch of height may be saved by the arrangement.

EVAPORATOR INLET CONFIGURATION (FIGS. 1, 7 and 10) In the conventional absorption refrigeration system utilizing circular, welded, tubular elements, the direction of flow of fluid components at junctions is controllable by providing an internal projection of one tube into another. Thus it is conventional practice in the circular, welded systems at the inlet of the evaporator to direct the incoming liquid refrigerant in the same direction as the relatively pure stream ofinert gas at the inlet of the evaporator. Such an arrangement is highly desirable to prevent a flow of liquid refrigerant in an upstream direction into the inert gas stream, which latter case would result in cooling taking place in the inert gas tube and gas heat exchanger rather than in the evaporator.

While possible, it is not compatible with the aim of the invention to open a tube in the panel or to provide any kind of an insert to insure that the liquid refrigerant is directed into the evaporator, rather than being permitted to back up into the inert gas line 30, to insure that the liquid refrigerant flows in the correct direction. The means for accomplishing this in accordance with this invention is best illustrated in FIG. 10 where it will be seen that an inverted trap generally designated 49 is provided in the portion of the carrier gas line 30 in the area of the evaporator inlet junction 29. The important aspect of the configuration shown in FIG. I0 is that the level of point 50 be higher than the level of point 51. With the general relationship of the lines forming the junction as shown, it is found to be inadequate to locate the point 50 at the same level as the point 51 since the capillary action with tubes of the size involved permits the liquid refrigerant to move into the carrier gas line 30.

It will be noted that a similar arrangement is shown in FIG. 7 in which the inverted trap is generally designated 49b.

In the arrangement of FIG. 8, since the carrier gas line 30c at the general location of the junction 290 is substantially above the condenser feed line 27c, the equivalent trap is effectively provided by the descent of the tube 300 to the junction 29c.

RESERVOIR (FIGS. 1 AND 12) All ammonia absorption systems of the inert gas type require a reservoir to provide ample liquid storage volume which serves both as a stabilizer for the operating concentration of the absorbent solution as well as providing a stable head potential for the thermosiphon pump. Because of the gravity flow from the absorber to the reservoir, the reservoir must be located below the absorber and should be of sufficient volume so that minor fluctuations in flow and orientation of the arrangement does not cause an unduly large variation in the liquid level, which in turn could adversely effect the rate of pumping. Also, the solution concentration should not change with small changes in pumping or delivery.

In applying some of these requirements to a panel type system, the limitations of the panel type system become relevant. Since the sheets of which the panel is formed are of a constant thickness throughout, it is not possible in the sheets themselves to reinforce the larger passage areas against the larger total rupturing forces encountered in the larger passage areas.

In accordance with the invention, the reservoir 17 is made in the form of an interconnected, multi-tube arrangement as shown in FIG. 1, or in a grid or waffle arrangement as shown in FIG. 12, in which bonded islands 53 are provided in a distributed pattern throughout the area of the reservoir.

The preferred arrangement is that shown in FIG. 1 in which the reservoir comprises a stacked series of horizontally extending tubes 54, 55 and 56, with interconnecting passages 57 near the ends of the tubes. The multi-tube arrangement of FIG. 1 is considered to offer the best design since the flow pattern through the successive tubes of the reservoir aids in mixing the liquid and reduces the tendency for liquid to stratify and cause a variation in concentration level between the tube 56 which receives the liquid, and the outlet end of the tube 54 connected to the rich ammonia liquid line 22 leading to the pump.

It will be noted that in both of the configurations of FIG. 1 and FIG. 12 of the reservoirs 17 and 17a, respectively, that the top portion of the reservoir also serves as part of the absorber section. The rich gas flowing through line 32 from the evaporator to the absorber may be compelled to pass over the top surface of the stored liquid in the reservoir 17a (FIG. 12) before passing up into the remainder of the absorber, as shown in FIG. 12, or a parallel entrance to a slightly higher level in the absorber may be provided as shown in FIG. 1 by the additional opening 36a. The parallel entrance 36a is considered useful in some instances to serve as a higher level inlet if the level in the reservoir for some reason rises sufficiently to provide an obstruction in the lower inlet 36. However, regardless of whether a single inlet 36, or a parallel inlet is used, to the extent that the rich gas flows across the surface of the liquid in the reservoir it is exposed to a larger liquid-gas interface which enhances the absorption process. Accordingly, the arrangement as shown serves not only to provide storage for the liquid and interconnecting passageway between the evaporator outlet and the absorber, but also serves as a pre-absorber section.

REVERSED BOILER AND PUMP SECTION (FIG. 13)

In this view the parts of the boiler and pump section are reversed relative to their arrangement in FIG. 1 but with the corresponding parts carrying numbers identical to those used in FIG. 1. Such an arrangement may be advantageously used where the height of the panel is limited. Another advantage with this arrangement is that the pump lift tube 21, which is the tube of smallest cross-sectional dimension of all of the tubes in the panel, is disposed with one of its bonded edges or sides adjacent the vertical edge of the panel. Since in some of the fabriccating techniques it is required that both of bonded edges of the tube 21 in effect be free of the remainder of the panel to achieve full inflation, the disposition of the one bonded edge of the tube adjacent the edge of the panel serves the same end.

As an example of the character of the dimensions involved in one reasonably satisfactorily panel of two sheet character and having a height in the order of 27-r inches and a width in the order of 21 inches, the tube widths range from about 0.260 inches to about 0.770 inches. The tube width is that dimension measured between the opposite bonded edges of a given tube and is indicated by the numeral 65 in FIG. 11. The tube of smallest width is the pump lift tube 21, while the tubes of greatest width are the reservoir tubes which have a width of 0.880 inches.

THREE SHEET PANEL (FIGS. 14-17) It is also considered to be within the scope of the invention to provide a complete absorption refrigeration system of the inert gas type fabricated of three metallic sheets superimposed upon each other, with the intermediate sheet having strategically located openings therein, and the inflation taking place in the two outer sheets. The openings in the intermediate sheet provide for internal crossovers from the tubes or conduits on one face of the panel to the tubes or conduits on the opposite face. This provides for a considerable saving in height, particularly in those fluid circuits which must traverse back and forth across the sheet since the three element composite allows the doubling back of a conduit by means of a hole pierced through the center sheet without a loss in height.

Before proceeding to a more detailed description of the more significant variants between the panels of FIG. 14 and FIG. 1 it is noted that the numerals used in FIG. 1 to designate particular parts are also used to designate the equivalent parts of the panel of FIG. 14.

It will be seen that the liquid refrigerant feed line 27 may pass in the same vicinity as the lines 30 and 32 making up the gas heat exchanger and then brought directly up by line to the inlet junction 29 of the evaporator, without being required to make a circuit all the way back around and to the top of the evaporator as in the case of the FIG. 1 arrangement.

Another particularly significant advantage afforded by the three sheet panel is found in the heat exchanger sections 14 and 17. In both arrangements the heat transfer takes place through the intermediate sheet and across the relatively large cross sectional area afforded thereby, and in contrast to the heat transfer in the two sheet panels in which the heat is transferred through the relatively small sectional area between conduits spaced one above the other. Thus, as shown in FIG. 15 dealing with the gas heat exchanger, the inert gas evaporator feed line 30 feeding inert gas upwardly toward the evaporator inlet 29 is on the left side of the sheet, while the evaporated refrigerant and inert gas mixture passes downwardly to the absorber through the line 32 on the opposite side of the center sheet.

As shown in FIG. 16, dealing with the liquid heat exchanger 17, the strong solution exit line 22 extending from the reservoir 16 over to the pump lift tube extends along the front of the center sheet, while the line 34 which carries weak solution to the absorber extends from most ofits length along the back side of the center sheet, and then may optionally be brought to the front side through the aperture 61 for its further passage upwardly to the top portion of the absorber.

The use of the three sheet panel with apertures also results in the holes in the center sheet serving as dams or weirs which, in the absorber (FIG. 17) at least, increases the effectiveness of the absorption.

While the cuts which serve as the thermal breaks are not shown in FIG. 14, it will be appreciated that they are located in accordance generally with those of the unit shown in FIG. 1. Also of course the evaporator section is displaced out of the general plane of the panel as discussed in connection with FIG. 1.

We claim:

1. In an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to effect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said components and all said passages lie in the general plane of said panel, said apparatus including an influx boiler construction formed as a unitary portion of said panel, said boiler construction including a vapor feed tube and a lift tube forming an intersection, both said tubes being generally elliptical in cross-section with the portions at the outer ends of the major axis extending beyond the normal curvature of an ellipse to form acute angle corners, the major axis of said feed tube at said junction being parallel to the longitudinal axis of said lift tube so that the upper one of said acute angle corners of said feed tube at said junction provides a restricted cross-sectional area passage, functionally equivalent to an orifice, above a substantially larger cross-sectional area serving as a pool from rich liquid is elevated up said lift tube.

2. In an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to effect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said components and all said passages lie in the general plane of said panel, at least one of said components comprises a serpentine arrangement of passages having return bends, and with successive passages being'oppositely inclined, the lower sides of at least some of said passages being provided with upwardly directed dams spaced therealong to prevent undisturbed flow along the lower side of said passages, with said dams includingone at the return bend end between successive passages, said one dam having a curvature in the direction of flow substantially the same as the curvature of said return bend and disposed to constitute a continuation of said return bend to reduce the vertical spacing between said consecutive passages.

3. in an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to ef' fect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said compo nents and all said passages lie in the general plane of said panel, said tube-in-sheet panel consists of three intially separate sheets before bonding, with the opposite outer sheets each including outwardly-bulging portions forming said components and passages, the intermediate sheet including selectively located openings to place selected ones of said components and passages on opposite sides of said intermediate sheet in communication.

4. An apparatus according to claim 3 including:

a gas heat exchanger and a liquid heat exchanger incorporated in said panel, at least one of said heat exchangers being formed of passages located substantially directly opposite each other on opposite sides of said intermediate sheet.

5. A tube-in-sheet panel containing a working fluid, the panel constituting the entirety of the flow system of an absorption'refrigeration system save for a source of heat to effect operation of said system, the panel being of generally rectangular outline and adapted to occupy a sufficiently upright plane during operation to accommodate the requisite gravity flow in the system, all of the refrigeration contributing components and connecting passages being in communication internally of said panel,

said panel including one area thereof having, in descending order and in generally vertical alignment, a condenser, evaporator, gas heat exchanger, absorber, receiver, and liquid heat exchanger, said panel further including another area on the general level of said absorber and reservoir and to the side thereof having a boiler and lift section,

said components and passages including;

an inert gas feed passage extending from the upper portion of the absorber to the inlet of said evaporator,

an evaporator exit passage connecting the outlet of said evaporator with the lower portion of said absorber, said inert gas feed passage and said evaporator exit passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said gas heat exchanger section,

a rich liquid passage extending from the lower portion of said reservoir to the lower portion of said boiler and lift section,

a weak liquid passage extending from the lower portion of said boiler and lift section to the upper portion of said absorber, said rich liquid passage and said weak liquid passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said liquid heat exchanger,

all of said components and passages lying in the general plane of said panel as formed,

an evaporator feed passage extends from the outlet of the condenser to the inlet of the evaporator,

the portion of said evaporator feed passage extends in adjacent heat exchange relation with said inert gas feed passage, and said evaporator exit passage and said panel includes slot means both above and below said evaporator, and extending generally horizontally to an edge of said panel to accommodate the displacement of at least said evaporator out of the general plane of said panel as formed for thermally isolating said evaporator from other portions of said panel without opening any of said passages.

6. A tube-in-sheet panel containing a working fluid,

the panel constituting the entirety of the flow system of an absorption refrigeration system save for a source of heat to effect operation of said system, the panel being of generally rectangular outline and adapted to occupy a sufficiently upright plane during operation to accommodate the requisite gravity flow in the system, all of the refrigeration contributing components and connecting passages being in communication internally of said panel,

said panel including one area thereof having, in descending order and in generally vertical alignment, a condenser, evaporator, gas heat exchanger, absorber, receiver, and liquid heat exchanger, said panel further including another area on the general level of said absorber and reservoir and to the side thereof having a boiler and lift section,

said components and passages including;

an inert gas feed passage extending from the upper portion of the absorber to the inlet of said evaporator,

an evaporator exit passage connecting the outlet of said evaporator with the lower portion of said absorber, said inert gas feed passage and said evaporator exit passage extending in counterflow, adjacent heat exchanger relation for a portion of their length to form said gas heat exchanger section,

a rich liquid passage extending from the lower portion of said reservoir to the lower portion of said boiler and lift section,

a weak liquid passage extending from the lower portion of said boiler and lift section to the upper portion of said absorber, said rich liquid passage and said weak liquid passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said liquid heat exchanger,

all of said components and passages lying in the general plane of said panel as formed,

said boiler and lift section comprises an influx boiler construction and includes a riser tube connected to a lift tube,

said riser tube and lift being arranged with said lift tube inboard of said riser tube,

said rich liquid passage extends from the side of said reservoir remote from said boiler and lift section to thelower end of said lift tube, said weak liquid passage extends from the lower end of said boiler on the outboard side of said rich liquid passage to the side of said absorber remote from said boiler and lift section.

7. In an influx boiler construction formed as a unitary portion of the tube-in-sheet panel absorption refrigeration system, a junction formed in said panel by the intersection of a vapor feed tube and a lift tube, both said tubes being generally elliptical in cross-section with the portions at the outer ends of the major axis extending beyond the normal curvature of an ellipse to form acute angle corners, the major axis of said feed tube at said junction being parallel to the longitudinal axis of said lift tube so that the upper one of said acute angle corners of said feed tube at said junction provides a restricted cross-sectional area passage, functionally equivalent to an orifice, above a substantially larger cross-sectional area serving as a pool for rich liquid refrigerant to be elevated up said lift tube. 

1. In an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to effect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said components and all said passages lie in the general plane of said panel, said apparatus including an influx boiler construction formed as a unitary portion of said panel, said boiler construction including a vapor feed tube and a lift tube forming an intersection, both said tubes being generally elliptical in cross-section with the portions at the outer ends of the major axis extending beyond the normal curvature of an ellipse to form acute angle corners, the major axis of said feed tube at said junction being parallel to the longitudinal axis of said lift tube so that the upper one of said acute angle corners of said feed tube at said junction provides a restricted cross-sectional area passage, functionally equivalent to an orifice, above a substantially larger crosssectional area serving as a pool from rich liquid is elevated up said lift tube.
 2. In an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to effect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said components and all said passages lie in the general plane of said panel, at least one of said components comprises a serpentine arrangement of passages having return bends, and with successive passages being oppositely inclined, the lower sides of at least some of said passages being provided with upwardly directed dams spaced therealong to prevent undisturbed flow along the lower side of said passages, with said dams including one at the return bend end between successive passages, said one dam Having a curvature in the direction of flow substantially the same as the curvature of said return bend and disposed to constitute a continuation of said return bend to reduce the vertical spacing between said consecutive passages.
 3. In an inert gas type, absorption refrigeration apparatus, a tube-in-sheet panel containing a working fluid to which a source of heat is adapted to be applied to effect operation of said apparatus, said panel comprising the entirety of the apparatus in the sense of providing a complete flow system including refrigeration contributing components and interconnecting fluid passages, save for said source of heat, said panel being constructed and arranged that as formed all said components and all said passages lie in the general plane of said panel, said tube-in-sheet panel consists of three initially separate sheets before bonding, with the opposite outer sheets each including outwardly-bulging portions forming said components and passages, the intermediate sheet including selectively located openings to place selected ones of said components and passages on opposite sides of said intermediate sheet in communication.
 4. An apparatus according to claim 3 including: a gas heat exchanger and a liquid heat exchanger incorporated in said panel, at least one of said heat exchangers being formed of passages located substantially directly opposite each other on opposite sides of said intermediate sheet.
 5. A tube-in-sheet panel containing a working fluid, the panel constituting the entirety of the flow system of an absorption refrigeration system save for a source of heat to effect operation of said system, the panel being of generally rectangular outline and adapted to occupy a sufficiently upright plane during operation to accommodate the requisite gravity flow in the system, all of the refrigeration contributing components and connecting passages being in communication internally of said panel, said panel including one area thereof having, in descending order and in generally vertical alignment, a condenser, evaporator, gas heat exchanger, absorber, receiver, and liquid heat exchanger, said panel further including another area on the general level of said absorber and reservoir and to the side thereof having a boiler and lift section, said components and passages including; an inert gas feed passage extending from the upper portion of the absorber to the inlet of said evaporator, an evaporator exit passage connecting the outlet of said evaporator with the lower portion of said absorber, said inert gas feed passage and said evaporator exit passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said gas heat exchanger section, a rich liquid passage extending from the lower portion of said reservoir to the lower portion of said boiler and lift section, a weak liquid passage extending from the lower portion of said boiler and lift section to the upper portion of said absorber, said rich liquid passage and said weak liquid passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said liquid heat exchanger, all of said components and passages lying in the general plane of said panel as formed, an evaporator feed passage extends from the outlet of the condenser to the inlet of the evaporator, the portion of said evaporator feed passage extends in adjacent heat exchange relation with said inert gas feed passage, and said evaporator exit passage and said panel includes slot means both above and below said evaporator, and extending generally horizontally to an edge of said panel to accommodate the displacement of at least said evaporator out of the general plane of said panel as formed for thermally isolating said evaporator from other portions of said panel without opening any of said passages.
 6. A tube-in-sheet panel containing a working fluid, the panel constituting the entirety of the flow system oF an absorption refrigeration system save for a source of heat to effect operation of said system, the panel being of generally rectangular outline and adapted to occupy a sufficiently upright plane during operation to accommodate the requisite gravity flow in the system, all of the refrigeration contributing components and connecting passages being in communication internally of said panel, said panel including one area thereof having, in descending order and in generally vertical alignment, a condenser, evaporator, gas heat exchanger, absorber, receiver, and liquid heat exchanger, said panel further including another area on the general level of said absorber and reservoir and to the side thereof having a boiler and lift section, said components and passages including; an inert gas feed passage extending from the upper portion of the absorber to the inlet of said evaporator, an evaporator exit passage connecting the outlet of said evaporator with the lower portion of said absorber, said inert gas feed passage and said evaporator exit passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said gas heat exchanger section, a rich liquid passage extending from the lower portion of said reservoir to the lower portion of said boiler and lift section, a weak liquid passage extending from the lower portion of said boiler and lift section to the upper portion of said absorber, said rich liquid passage and said weak liquid passage extending in counterflow, adjacent heat exchange relation for a portion of their length to form said liquid heat exchanger, all of said components and passages lying in the general plane of said panel as formed, said boiler and lift section comprises an influx boiler construction and includes a riser tube connected to a lift tube, said riser tube and lift being arranged with said lift tube inboard of said riser tube, said rich liquid passage extends from the side of said reservoir remote from said boiler and lift section to the lower end of said lift tube, and said weak liquid passage extends from the lower end of said boiler on the outboard side of said rich liquid passage to the side of said absorber remote from said boiler and lift section.
 7. In an influx boiler construction formed as a unitary portion of the tube-in-sheet panel absorption refrigeration system, a junction formed in said panel by the intersection of a vapor feed tube and a lift tube, both said tubes being generally elliptical in cross-section with the portions at the outer ends of the major axis extending beyond the normal curvature of an ellipse to form acute angle corners, the major axis of said feed tube at said junction being parallel to the longitudinal axis of said lift tube so that the upper one of said acute angle corners of said feed tube at said junction provides a restricted cross-sectional area passage, functionally equivalent to an orifice, above a substantially larger cross-sectional area serving as a pool for rich liquid refrigerant to be elevated up said lift tube. 